Tube rolling mill for producing tubing with various internal configurations

ABSTRACT

A tube rolling mill having two sets of three rolls each which are reciprocatingly driven along a length of a tube supported by a mandrel. Each roll is forced against the tube by individual cams that each have a surface of one or more tapers to provide controlled reduction in wall thickness of the tube. The mandrel is tapered to provide a reduction of inside tube diameter and is of a configuration to cause the inside wall of the tube to be shaped as for example in hexagonal form, simultaneously as the inside tube diameter and wall thickness are reduced. Various inside wall configurations may be produced such as clover leaf shapes, flat sided configurations, ovals, and a combination of circular and flat surfaces, each of the patterns running for the length of the finished tube.

United States Patent 1191 Bibigltaus June 4, 974

[54] TUBE ROLLING MI L F R RO U N 3,611,775 10/1971 Gabel et al. 72/193TUBING WITH VARIOUS INTERNAL CONFEGURATHONS Primary ExaminerMilton S.Mehr Attorney, Agent, or FirmWoodc0ck, Washburn, [75] Inventor. W.Bibighaus, Wapakoneta, Kurtz & Mackigwicz [73] Assignee: Superior TubeCompany, [57] ABSTRAQT Norrismwn A be 11' '11 h t ts f m 11 h tu ro mgm1 avmg wo se 0 rec ro s eac [22] Wed: 1972 which are reciprocatinglydriven along a length of a [2]] A L N 298,616 tube supported by amandrel. Each roll is forced against the tube by individual cams thateach have a surface of one or more ta ers to rovide controlled [52] US.Cl. 72/208, 72/214 reduction in wall thickness s the g The mandrel is 1Hllll. tapered to provide a reduction f inside tube diameter [58] Fleld0: Search 72/209 and is of a configuration to cause the inside wall ofthe 72/224 220 tube to be shaped as for example in hexagonal form,simultaneously as the inside tube diameter and wall [56] References andthickness are reduced. Various inside wall configura- UNITED STATESPATENTS tions may be produced such as clover leaf shapes, flat 185.37412/1876 Whitehouse 72/208 sided configurations, ovals, and a combinationof cir- 1,413,604 4/1922 Okano cular and flat surfaces, each of thepatterns running 2,568,730 9/195] Guthmann for the length of thefinished tube 3,! 18,328 l/l964 lssott 3,354,682 1 1/1967 Dupuy 8Claims, 14 Drawing Figures TUBE ROLLING MILL PRODUCING TUBING WITHVARIOUS INTERNAL CONFIGURATIONS BACKGROUND OF THE INVENTION The subjectinvention improves upon and develops further in somerespects theteachings of US. Pat. No. 3,688,540 which issued Sept. 5, 1972; US. Pat.No. 3,683,661 which issued Aug. 15, 1972; and U.S. Pat. No. 3,611,775which issued Oct. 12, 1971.

This invention relates generally to a method and apparatus for reducingand elongating metal tubing and more particularly to a method andapparatus for producing tubing which has its interiorwalls shaped intovarious configurations by a cold rolling tube reducing process.

Metal tubing is used in a wide variety of environments and for manydifferent applications. This requires that tubing be abailable with awide variety of inside and outside diameters and wall thicknesses.Furthermore, certain applications require that the tubing be providedwith various internal configurations. In order to effectively utilizethe economies of mass production, metal tubing is initially manufacturedin only a few standard cylindrical sizes. This makes it necessary tomodify tubing of a standard manufactured size to obtain a finished tubehaving an overall size that is needed for a certain applicationrequiring less tubing that can be economically manufactured directly.When it be comes necessary to shape the tubing into various internalconfigurations, and this operation is in addition to the reducing andsizing operation, the overall production of such tubing becomes costly.

A machine for reducing tubing of a standard manu factured size with tworolls and a mandrel is described by Krause in the Iron and SteelEngineer, August, 1938, pp. 16-29, and in several patent publicationssuch as US. Pat. Nos. 2,161,064, 2,161,065 and 2,223,039. In addition,there have been several disclosures by the Argonne National Laboratoriesrelating to similar machines. Also, several publications by Russianauthors have described tube rolling mills having three or six rolls.However, none of these disclosures suggest a practical way of producingtubing in which the inside walls are configurated and shaped by a coldrolling process.

Therefore, it is an object of this invention to provide a tube rollingmill capable of producing various configurations on the interior wallsurface of tubing.

It is also an object of this invention to provide a method of producingconfigurations on the interio wall surface of tubing by cold rolling.

lt is a further object of this invention to provide a method andapparatus for producing configurations on the interior wall surface of atube simultaneously and as part of a process of reducing the tubes wallthickness and/or its inside diameter.

SUMMARY OF THE lNVENTlON around its outer circumference to producecylindrical tubing or may have substantially flat surfaces to produceflat sided tubing. The plurality of rolls is held by .a common rollhousing which is reciprocated along the length of the tubing. Cam guidemeans are provided for the rolls so that they exert a substantial amountof pressure against the tube. It is this pressure against the tube whichcauses metal of the manufactured tubing to flow into a desired newshape. The plurality of rolls are positioned so that their tubecontacting grooves or flat surfaces surround the tube being reduced.

In a preferred form of the invention, three rolls are utilized in acluster about the tube with their axes of rotation located in a planesubstantially perpendicular to the tube and displaced from each other.Each roll is rotatably attached to a roll housing. The roll is urgedagainst the tube by a pair of cam tracks on which roll trunnions ride.Within the roll housing, means are provided to insure that the rollscontact the cams at all times. I

As described hereinafter, the interior walls of the tube are shaped intovarious desired configurations in conjunction with either wall thicknessor inside diameter reduction, or both, to obtain an internallyconfigurated tube that is dimensioned exactly as required for aparticular application. ln order to obtain a good quality tube witheither wall thickness or inside diameter reduction, or both, it ispreferred to use two sets of three roll clusters with a fixed spatialrelationship within a roll housing. The axes of rotation of the rolls ofone set (cluster) are displaced 60 from the axes of rotation of therolls of the other set.

The tube is'worked on a tapered mandrel which may be tapered todifferent degrees along its length which will cause the inside diameterof the tube to be reduced. As this reduction is taking place, shaping ofthe internal wall of the tube into various configurations may also becarried out by the use of a tapered mandrel with various shapes groundupon it in the following manner. Each mandrel has a portion with adiameter slightly less than the inside diameter of the tube to bereduced. From this point the mandrel tapers either fairly abruptly or ina series of tapers to a point where the final sizing diameter isobtained. The mandrel has ground into it shapes which will be transposedonto the inside wall of the tube as it is reduced, the mandrel servingas an interior mold. At the sizing portion of the mandrel, theconfiguration of the mandrel is exactly as will be transposed to theinterior of the tube as the tube is rolled over the mandrel. From thissizing portion of the mandrel to the larger portion of the mandrel whichis slightly less in diameter than the original piece of tubing that isbeing reduced in shape, the configuration which is ground into themandrel becomes less and less pronounced and reaches a point where theconfiguration disappears and the cylindrical mandrel shape prevails. Inother words, as the mandrel tapers towards its sizing position theground configurations become more and more pronounced which effectivelyenables the tubing to be rolled onto the configurated mandrel and beshaped and dimensioned according to the mandrel I shape at its sizingsection.

Various inner diameter configurations may be produced such as hexagonaland triangular shapes, shapes having a ridged area or'a grooved area andoval and clover-leaf type patterns. The hexagonal and flat sided shapesare produced by having a mandrel with flats extending lengthwise asabove described along the mandrel from the sizing area graduallybecoming less pronounced until the largest cross-sectional portion ofthe 3 mandrel is reached where the mandrel shape becomes cylindrical.

Tubes having spiral configurations on the interior are also desired andthese may be produced by using spiraled mandrels in, for example, ahexagonal or triangular pattern.

Numerous uses may be made of the configurated tubing, a few of whichwill be listed. The flat sided tubing as for example decagonal tubingmay be used to form a suitable bore for 8-8 guns. Hexagonal and variousshapes such as triangular and square shaped tubing may be used forsocket wrenches and the like. Tubing of a clover-leaf pattern may haveapplication in heat exchange processes which will be described later.

Internally configurated tubing may be produced by the techniques of thepresent invention with a wide va riety of metals including thoseconsidered generally hard to work such as stainless steel, AIS! types of304 and 3 I6.

The techniques of the present invention are de scribed in more detailhereinafter with respect to the drawings which show a preferredembodiment utilizing two roll clusters of three rolls each and taperedmandrels of various configurations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified partiallyexploded view showing essential elements ofa rolling mill in which thesubject invention is utilized;

FIG. 2 is a cross-sectional view of FIG. 1 taken through the first stage(set) of rolls at 22;

FIG. 3 is a cross-sectional view of FIG. 1 taken through the secondstage (set) of rolls 3-3;

FIG. 4 schematically illustrates the operation of the primary operatingcomponents of the rolling mill illustrated in FIGS. 1, 2 and 3;

FIG. 5 shows the shape ofa preferred tube contacting groove of a rollfor use in the rolling mill shown in FIGS. 1-3;

FIG. 6 is a front elevational view showing a mandrel having a hexagonalshape;

FIGS. 7a 7b, and 7c are cross-sectional views of FIG. 6 taken along thelines Ia-7a, 711-712, and "iv-7c;

FIG. 8 depicts a mandrel having a groove which is used to produce tubingin which the inner wall has a ridge along its length;

FIG. 9 is a cross-sectional view of the mandrel of FIG. 8 taken alongthe lines 99;

FIG. 10 is a front elevational view ofa spiral mandrel at the sizingsection of the mandrel;

FIG. 10a is a cross-sectional view of HG. 111 taken along lines 10-11);and

FIG. 11 shows cross-sectional views of tubing A through K which may beproduced by mandrels within the contemplation of the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a camhousing 11 is reciprocatcd relative to a machine frame 13 along a slide15 in substantially a straight line. An electric motor 17, also attachedto the frame 13, drives a flywheel 19. A rod 21 (partially broken away)is connected between the flywheel 19 at a crank pin 20 and the camhousing 11 to convert rotary motion of the flywheel to reciprocablemotion ofthe cam housing. Within the cam housing 11 is a reciprocatableroll housing 23, shown removed from the cam housing for clarity ofillustration. A pinion gear 25 engages a rack 27 that is rigidlyattached to the frame 13. A second pinion gear 26 engages a rack 29 thatis rigidly attached to the cam housing 11. The pinion gears 25 and 26are concentric about a common axis of rotation 311 and are nonrotatablerelative to each other. The reciprocable motion of the axis of rotation311 of the pinion gear 25 is communicated to the roll housing 23 bymeans of a connection rod 31 (shown herein as two sections since theroll housing 23 is shown removed from the cam housing 11). The camhousing 11. has a maximum reciprocation stroke distance that is equal tothe diameter of the circular path taken by the crank pin 2d. From thegeometry of the driving arrangement of FIG. 1, the roll housing 23 has amaximum reciprocation stroke distance that is equal to the maximumstroke of the cam housing 11 multiplied by the diameter of the piniongear 25 and then divided by the sum of the diameters of the pinion gears25 and 26. The use of two pinion gears having different radii as hereindescribed has the effect of increasing the length of the working zonealong the tube without increasing the stroke length of the cam housing.It should be noted that although the double pinion gear arrangementherein described is very convenient for controlling the maximum relativecam housing and roll housing stroke distances, and thereby theirrelative velocities, other specific mechanical arrangements, such as oneemploying levers, may also be employed for the same purposes.

Another aspect of the geometry of this arrangement in FIG. 1 is that thecam housing stroke distance is equal to the sum of the roll housingstroke and the working stroke length of the cams (the distance alongeach cam that contacts a roll trunnion) within the cam housing. itfollows, then, that the cam length contacted by each roll bears the samerelationship to the roll housing stroke as a ratio of the diameter ofthe cam housing pinion gear 26 to the diameter of the roll housingpinion gear 25.

A tube 33 to be reduced is inserted through an opening 35 of the rollhousing 23., and is carried by a mandrel 37 which is held fixed relativeto the machine frame 13 though rotatable by an appropriate grippingdevice 36., which also provides for removing the mandrel and includesthe means for rotating the mandrel. An appropriate apparatus 38 isprovided for positively gripping the tube 33 and linearly advancing(feeding) it over a working length of the mandrel 37. The apparatus 38can also be designed to rotate the tube at specific positions of thereciprocating cycle in order to produce smooth tubing having a smoothexternal surface of reduced size. In order to produce tubing withconfigurated inner walls in'accordance with the present invention, themandrel is rotated as the tube is rotated.

FIGS. 2 and 3 better show the relationship of tube deforming rolls andthe cam housing as sectional views of FIG. 1. A first set of rolls 39,411 and 43, shown in FIG. 2, are held in the roll housing 23 with theiraxes of'rotation lying substantially in a plane perpendicular to themandrel 37 and making an angle of with each other. Similarly a secondset of rolls 45, 47 and 49, shown in FIG. 3, are held by the rollhousing 23 in the position that their axes of rotation liessubstantially in a plane perpendicular to the mandrel 37 and at aspatially fixed distance along the length of the mandrel from the planein which the axes of rotation of the first set of rolls 39, 41 and 43lie. Furthermore, the axes of rotation of the two sets of rolls areangularly displaced from each other by 60.

Although held by the roll housing 23 against movement relative theretoin the direction of its reciprocation, each roll is free to move in adirection normal to the mandrel. Each roll is resiliently urged by a setor springs (such as springs 49 and 50, each held within a roll guide)out of the roll housing 23 and against its associated'cam surfaces.Alternatively, the rolls may be hydraulically urged against theirassociated cams. Each roll has a trunnion formed on either side thereof,such as trunnions 51 and 53 on either side of the coil 45. Each roll isassociated with a pair of cam tracks upon which its pair of trunnionsride. The two cams associated with each roll are designated herein withthe same number as the roll but with an asterisk placed after thereference number of one of the cam tracks and a double asterisk placedafter the number referring to the other of the cam tracks. The cams arelong metal bars shaped in a manner discussed hereinafter and rigidlyattached to the cam housing 11. This attachment is accomplished througha recessed member for each pair of cams, such as a recessed member 55which is shaped to support the cams 45* and 45**. Notice that the cams45* and 45** each have a sloped side surface which allows fastening themto the recessed member 55 by a wedge 57 which is attached to therecessed member by a threaded fastener 58.

It should be noted with reference to FIGS. 1, 2 and 3, the ease withwhich the cam surfaces may be replaced in the cam housing ll and alsothe ease with which the rolls may be replaced in the roll housing 23.

A given pair of cams are removed by removing their associated wedge. Therolls are merely lifted out of the roll housing 23 when the roll housingis removed to a position as illustrated which is out of the cam housing11. The mandrel 37 is also easily removed. These features allow quickconversion of the tube rolling mill to receive raw tubes of varioussizes and also to produce finished tubes with various wall thicknessesand inside diameters.

The schematic diagram of FIG. 4 illustrates operation of the rollingmill illustrated in FIGS. 1, 2 and 3. A mandrel 37 which is not shapedfor the purpose of producing configurated tubing walls in accordancewith the subject invention but which may be used for illustrativepurposes is shown in cross-section along its length which includes atube working zone B-J wherein at all points therealong the tube 33 iscontacted by one or both sets of rolls to accomplish reduction either inwall thickness or inside diameter or both. The mandrel has a diameter d,at its large end which is something slightly less than the insidediameter of the starting tube 33, thereby allowing the tube to he slideasily over the mandrel. The small end of the mandrel has a diameter (1which is substantially equal to the desired inside diameter of thereduced tube. The mandrel 37 is gradually tapered within the tubeworking zone from one of these diameters to the other. This taper issignificantly in excess of that required for tube relief. The diametersd, and d may differ by or or more, depending on the tube inside diameterreduction desired.

In order to demonstrate the cooperation between the cams and the.mandrel, one roll from each of the two sets of rolls is shown in FIG. 4as if they operated in the same plane so that the relationship betweenthem and their cooperation in reducing the tube are illustrated. Rolls39 and 45 are illustrated in FIG. 4 along with their associated earns39* and 45*, respectively. The axis of the first stage roll 39reciprocates along the tube between positions A and I with a distancetherebetween equal to the stroke distance of the roll housing 23 (notshown in FIG. 4) in which the roll 39 is journaled. Similarly, the axisof the second stage roll 45 reciprocates along the tube betweenpositions D and K. The cams 39* and 45* are attached to the cam housing11 (not shown in FIG. 4) and'thereby are reciproeatably driven at agreater velocity than the axis of the rolls, as described hereinabove.The cam 39* contacts a trunnion attached to the roll 39 and the camcontacts the trunnion 51 of the roll 45. The shape of the cams and ofthe mandrel determine the displacements of rolls downward against thetube to bring about a desired deformation of the tube.

Consider a single working stroke wherein the rolls and earns of FIG. 4move from their far left hand position to the far right and back again.This represents the extent of movement brought about by a singlerevolution of the flywheel 19 of FIG. 1. The roll 39 begins at theposition A and the roll 45 begins at the position D. As shown by thedashed lines, the roll 39 contacts the tube 33 for the first time atabout the position B and the roll 45 contacts the tube 33 for the firsttime at approximately the position F. Proceeding further to the right,the cooperative shapes of the cams and the mandrel allow the roll 39 tobe lifted from the tube 33 at about the position F, as shown by the path[39] of the roll, away from the tube. Similarly, the roll 45 is causedto be lifted from the tube 33 at about the position J, as shown by thepath [45] of the roll, away from the tube.

The roll 39 arrives at the position I at the same time the roll 45arrives at the position K to complete the first one-half of the workingstroke. The rolls 39 and 45 then move back to their beginning positionsA and D, respectively, to complete one working stroke cycle. It. may benoted that the cam working length as used herein is a horizontalprojection of the length of a cam surface contacted by the trunnion.With reference to the cam 39*, the cam working length thereof is thehorizontal distance between points A, and I The tube 33 is advanced(fed) by the apparatus 38 an increment to the right while the rolls aredrawn away from contact with the tube, either at one or both ends of theworking stroke. As a variation in the system shown in FIG. 4, the earns39* and 45* may be altered so that the rolls 39 and 45 are not drawnaway from the tube at positions I and K, respectively. and the tube isfed only at the beginning of the working stroke. The shape of the tube33 shown in FIG. 4 within the workingzone represents the finished shapethereof after working stroke and before the tube is fed an increment inpreparation for the next working stroke.

There are many specific cam and mandrel shapes that may be utilizeddepending upon the specific tube reduction desired. FIG. 4 illustrates apreferred arrangement for major inside diameter reduction. The followingtabulation describes the work done by the roll 39 within the workingzone between lettered positions along the length of the tube;

Between B-C: The tube is reduced to intimate contact with the mandrel.

Between C-E: Primarily tube diameter reduction is accomplished by theroll 39.

Between E-F: Primarily wall reduction is accomplished by the roll 39.

The following tabulation describes the work concurrently performed'bythe roll 45 within the working zone between letter positions along thelength of the tube:

Between F-Gz Primarily wall reduction performed by the roll 45.

Between G-H: Primarily wall reduction performed by the roll 45 but witha lesser bit into the tube than between F-G.

Between H-J: This is a finishing zone where there is substantially notaper to the mandrel 37 and with very little bite of the roll into thetube.

To accomplish the above-noted specific tube reductions at various pointswithin the tube working zone, the mandrel has one or more straight linetapers. The cams are shaped cooperatively therewith, each having aplurality of straight line tapers. The cams of FIG. 4 have their rollcontacting surfaces marked with subscripted letters corresponding to thelettered positions along the tube. For example, when the roll 39 uspositioned at E along the tube, the cam 39* is contacting the trunnionat position E Straight line-tapers are preferred for the cams and themandrel since they are easy to machine, although continuous curves mayalso be employed.

The description herein with respect to FIG. 4 is ex emplary only withvarious changes in the specifics thereof being possible. For example, ifmajor inside tube diameter reduction is not required, the portion B F,of the cam 39* may be shaped differently relative to the portion B-F ofthe mandrel than as shown to effect tube wall reduction between BFinstead of the tube diameter reduction. Also, the elements may bedesigned so that the rolls 39 and 45 overlap in their work zones along aportion of the tube, preferably with dissimilar cam tapers acting on thetwo rolls in this common length of the tube. Also, certain applicationsmay require only a single taper along a working length of each of oneset of cams.

Along any of the portions of the tube length wherein substantial wallthickness reduction is desired, the controlling cam and mandrel tapersare designed for a bite of the rolls into the tube at each point withinthis portion that is approximately the same percentage of the wallthickness at that point before the roll. Multiple straight line taperson the cams may be employed to ap-.

proximate this constant percentage although continuous curved camsurfaces are more exact. The amount of tube feed for each stroke is thenadjusted to a maximum for a given tube material just short of that whichruptures the tube, thereby maximizing productivity of I the machine.

A preferred tube contacting groove is illustrated in FIG. 5 for therolls of a rolling mill illustrated with respect to FIGS. 1-3. Thegroove shape is uniform in cross-section at any radial plane thereof.The groove cross-section is shown on a roll 79 which represents relativeroll groove dimensions for any roll shown in FIGS. 1-3 for the purposeof describing roll groove design. In the center of the groove is anarcuate portion 8l having a center of curvature at a point 83. Joiningeither side of the arcuate center portion 81 as tangents thereto at itsend points 85 and 87 are straight line segments 89 and 91 which extendto the groove outside edges 97 and 99, respectively. The arcuate portion81 extends for an angular distance 15 on either side of a center line.

Theradius of curvature of the arcuate portion 81 is made substantiallyequal to or slightly less than the smallest outside tube radius the rollis designed to contact, such outside tube radius being represented by asolid circle 93. This represents a desired radius of the finished tubefor the roll 45 shown in FIG. 4 and the ra dius of the tube at locationF for the roll 39. A circle (FIG. 5) represents the largest outside tuberadius which the roll groove is designed to contact, that of thebeginning tube for the roll 39 of FIG. 4 and that of the tube atposition F for roll 45.

This roll groove design provides two zones of contact for each rollagainst the outside of the tube between the tubes larger portion (95)and substantially until its smallest portion (93). Such two-zone rollingaccomplishes more reduction in a given working zone of a tube whencompared to a roll groove providing only one Zone of contact with thetube. Non-uniform tube wall strain is reduced as well as resultingdegradation of tube quality. Also, required rolling forces, and thusmachine wear, are reduced. To optimize these advantages, the radius ofthe arcuate center portion 81 of the roll groove may be made 1 or 2percent less than the smallest outside tube radius to be contracted bythe roll groove, thereby extending two zone rolling over the entirelength of the tube contacted by the roll, whereby roll life is extended.FIG. 5 illustrates such a preferred roll that is designed to contact thetube at two zones throughout the stroke. A rolling radius r of the roll79 along the tube varies between R,, (contacting tube portion 95) andR,,,,-,, (contacting tube portion 93) during each tube reducing stroke.An arcuate center portion 8i with a radius significantly smaller thanthe finished tube outside radius (in the extreme the groove becomesV-shaped) results in a finished reduced tube surface that is irregularand rough.

For a given tube material, there is an optimum angle 0,: which allowsthe roll to take the most efficient maximum bite into the tube, therebyresulting in the most rapid feed rate of the tube through the machine.An angle qb of from 30-38 is satisfactory for most common tube materialsand specific types of reduction.

The tangential portions 89 and 91 of the roll groove are shown in FIG. 5as straight lines. However, these portions of the groove may,alternatively, be given a curvature with one or more finite radii ofcurvature.

The rolling mill described with respect to FIG. 4 is used for producinga smooth surface finished tube by rotating the tube at least once eachworking stroke at a position thereof where the rolls do not contact thetube.

In accordance with the subject invention, in place of the taperedcylindrieal-in-cross-section mandrel described above there issubstituted a configurated mandrel which is tapered and has ground intoit, a shape which suitably forms an internal mold for the tube beingprocessed, the mold being transitional in nature so that the internalshape of the tube is gradually transformed as it is rolled fromcylindrical-in-shape to its desired shape. As the tube is rotated aftereach working stroke (the amount of rotation being variable) the mandrelis also rotated in like manner as the tube to permit the continualforming of the internally shaped tube through successive workingstrokes.

With reference to FIG. 6, a mandrel is shown for producing tubing havinghexagonal inner walls. The mandrel 170 has six flats 171 or flat sideswhich produce a mandrel which is hexagonal in cross-section at thesizing portion as shown by the cross-sectional view in FIG. 7a. To theright of this sizing section, the mandrel continues to taper in slightdiminution of size to provide the relief area to enable easy removal ofthe tube when the rolling process has been completed for the particularsection of tubing which had been rolled. The hexagonal configuration ismaintained and the relief area consists of the six flat sides or reliefflats.

The diameter of size of the'mandrel 170 increases to the left side ofthe sizing portion to the far left where the greatest diameter of themandrel is located. It will be noted that the flat sides I71 graduallytaper to zero along this portion. As configuration 7a shows, thecross-sectional area at the sizing section is a hexagon formed by sixflat sides 171A while FIG. 7b taken midway between the sizing sectionand the left end of the mandrel shows a figure which is characterized bysix flat portions 171B and six rounded portions 1748 as the gradualreduction of the flat sides occurs. As FIG. 70 shows, thecross-sectional area of the mandrel 170 at the point where the flatsdisappear almost completely comprises small flat portions 171C andincreased rounded portions l74. The tube working zone as described inrelation to FIG. 4 extends from the left of section line 70 in FIG. 6 tothe tube sizing section represented by section line 7a. Thus, theinitial rolling commences at a point where the mandrel is at itsgreatest diameter and perfectly cylindrical in cross-section. Themandrel 170 is secured by means 172 in the manner of a cylindricalmandrel 37 as described in the general description.

With reference to FIG. 8, a mandrel 175 is shown which may be used forproducing tubing having a ridge on its inner wall. The mandrel 175 has agroove 176 which extends from the relief end of the mandrel at the rightside and gradually decreases in depth as the diameter of the mandrelincreases to a point where the groove disappears completely on the leftside of the mandrel near where the mandrel is at its largest diameter asshown by reference numeral 177. This is at the approximate location ofthe beginning of the working zone as described with respect to FIG. 4.As shown in FIG. 9, the sizing section ofthe mandrel is circular and hasthe one groove into which the metal tubing flows as it is cooled rolledon the mandrel.

With reference to FIG. 10, a further embodiment of a hexagonal type ofmandrel 190 is illuatrated. In this embodiment the flats 191 which makeup the hexagonal sides are spiraled or rifled to produce a spiralingeffeet in the rolled tubes. The spiraling may be such that there is one360 turn in 20 inches of length. As in the embodiment of FIG. 6, theflats I91 begin to emerge from the cylindrical position of the mandrel190 slightly to the right of the beginning of the tube working zone asshown in FIG. 4. The flats 191 increase in size as they extend to theright causing more and more of the cross-sectional surface of themandrel to be covered by flat portions, and prior to the time where theflats I91 reach the sizing section a hexagon is formed, thus producingthe hexagonal sizing section as is shown in FIG. 10A. The spiraledmandrel 190 of FIG. 10 is similar to the mandrel 170 of FIG. 6 exceptfor the spiraling and if the sizing end of mandrel 170 could be twisted,mandrel could be produced. As in the case of the previously describedmandrels, the area to the right of the sizing section is a relief areawith a reduced size to enable the tube to be removed from the mandrelonce it has been rolled to the size and shape of the mandrel at thesizing section.

As shown in FIG. 11, cross-sectional views of various tubes which can beproduced by shaped mandrels are shown. The present invention should notbe considered as limited to the configurations shown in FIG. 11 sincemandrels may as well be ground to' produce various other internalconfigurations. Numerous applications may be made of the shaped tubingshown in FIG. 11 including the following uses. The tubing of FIG. 1111has particular utility in heat exchange applications. A round tube maybe placed inside of the center portion of the clover-leaf while theoutlying areas effectively form separate conduits which can be used toadvantage where heat exchange principles are involved. For example,fluid may be. supplied in the inner round tube while other fluid or agas may be supplied in the outer conduits for the purpose of exchangingheat from one to the other.

The tubing of FIG. 11k which is in the shape of a decagon may be usedadvantageously as to produce barrels for BB guns and air rifles, and thelike. the flat sides or flats being necessary to impart spin in the BB.

The tubing of FIG. 11d is internally configurated into the shape of ahexagon and such tubing finds utility when cut and manufactured intovarious size socket wrenches and the like. Other of the configurationssuch as the tube of FIG. Ila have electronic applications and presentthe user of the tubing with a wide range of products to meet variedneeds.

Thus, tubing having various internal configurations may be produced bycold rolling a cylindrical tube on a tapered mandrel which has beenground to provide the desired shape to be molded into the tube. Themandrel may be made of a Vasco 350 steel which is an 18% nickel, chromesteel. Flats, grooves, and the like may be ground into the mandrel sothat they begin to emerge near the end of the mandrel where the diameteris the greatest and gradually increase in size until they reach thedesired size for molding near the sizing point of the mandrel. Grinding,for example, flats, may be done by grinding the flat at the sizing endand continuing to grind back along the mandrel on a taper until the flatdisappears.

By the use of a tapered mandrel which has various shapes ground into itas described above, tubing having various internal configurations may beproduced during a rolling process in which the inner diameter of thetube is sumultaneously reduced as the shaping is being done. The tubingwill assume the shape of the mandrel and the interior of the tube willthus be converted to have a configurated inner wall with grooves, flats,ridges or the like running the length of the tubing. Since both the tubereduction and the tube shaping as described above can be performedsimultaneously as distinguished from previously known processes in whichtwo distinct operations were necessary, higher production may beachieved and operational expenses accordingly reduced.

It shall be understood that the invention is not limited to the specificarrangements described herein and the preferred embodiments, but thatchanges and modifimade within the scope of the appended claims.

What is claimed is:

l. A mandrel for use in a cold rolling process in which cylindricaltubes are simultaneously reduced and shaped to assume various internalconfigurations, said mandrel comprising:

a first length where said mandrel is cylindrical and of a diameterslightly less than the inner diameter of the tube to be shaped,

a second length where said mandrel is of a size and shape to serve as aninterior mold about which the tube is rolled to assume its finished sizeand shape,

a continuously tapered transitional length joining said first and secondlengths along which said mandrel shape gradually is developed from saidfirst length to said second length so that the tube may be rolled over aworking zone of said mandrel ex tending from said first length to saidsecond length whereby during the time of rolling the tube will graduallybe reduced and shaped as it is rolled over said transitional lengthuntil the tube assumes the shape and sizing of the second length of saidmandrel, and

a relief length at its end adjacent to said second length, said relieflength tapering slightly but otherwise conforming to the shape of thesecond length to permit removal of said tube once it has been rolled toassume the configuration of the second length of said mandrel.

2. The mandrel of claim 1 wherein the shape of the second lengthcomprises longitudinal flat portions which extend into the transitionallength where they gradually become less and less in width to a pointwhere they taper to zero in the proximity of the first length of saidmandrel which is cylindrical.

3. The mandrel of claim 2 wherein the second length comprises sixlongitudinal fiat portions which cover the entire outer surface of saidsecond length of said mandrel to provide an interior mold for forming ahexagonal tube, said six longitudinal flat portions gradually taperingto zero through said transitional length of said mandrel. the totalcross-sectional area of said transitional length tapering in theopposite direction to said flat portions to provide the transitionallength with a combination of rounded and flat portions runninglongitudinally throughout said transitional length said rounded portionstapering toward said second length while said flat portions tapertowards said first length.

4. The mandrel of claim 3 wherein said longitudinal fiat portions arespiraled through at least said transitional length to provide a tube ofspiraled hexagonal configuration.

5. The mandrel of claim 2 wherein the second length comprises threelongitudinal flat portions which cover the entire outer surface of saidsecond length of said mandrel to provide an interior mold for forming atriangular tube, said three longitudinal flat portions graduallytapering to zero through said transitional length of said mandrel, thetotal cross-sectional area of said transitional length tapering in theopposite direction to said flat portions to provide the transitionallength with a combination of rounded and flat portions runninglongitudinally throughout said transitional length said rounded portionstapering toward said second length while said fiat portions tapertowards said first length.

6. The mandrel of claim 5 wherein said flat portions are spiraled toprovide a tube which is of spiraled triangular configuration.

7. The mandrel of claim 1 wherein said mandrel has a groove in itssecond length which gradually diminishes in depth through saidtransitional length of said mandrel to a point where said groove reacheszero depth in the proximity of said first length of said mandrel, saidgroove causing the formation of a ridge on the inner wall of said tubeas it is rolled over the working zone of said mandrel.

8. A mandrel for use in cold rolling processes to produce tubing withvarious internal configurations comprising:

an elongated member adapted for insertion within a hollow circular tube,said member being tapered and shaped for at least portions of itslength, said shaping being for the purpose of imparting to the interiorwalls of the hollow circular tube the shape of said mandrel, saidshaping comprising surfacing of said mandrel so that said mandrel iseffectively divided into longitudinal portions, each portion being ofthe same configuration, although gradually increasing in size andpronouncement from the end of the mandrel of greatest diameter to theopposite end near the portion of the mandrel where the size and shape ofsaid mandrel are used to mold the interior walls of said tube.

l l= l =l

1. A mandrel for use in a cold rolling process in which cylindricaltubes are simultaneously reduced and shaped to assume various internalconfigurations, said mandrel comprising: a first length where saidmandrel is cylindrical and of a diameter slightly less than the innerdiameter of the tube to be shaped, a second length where said mandrel isof a size and shape to serve as an interior mold about which the tube isrolled to assume its finished size and shape, a continuously taperedtransitional length joining said first and second lengths along whichsaid mandrel shape gradually is developed from said first length to saidsecond length so that the tube may be rolled over a working zone of saidmandrel extending from said first length to said second length wherebyduring the time of rolling the tube will gradually be reduced and shapedas it is rolled over said transitional length until the tube assumes theshape and sizing of the second length of said mandrel, and a relieflength at its end adjacent to said second length, said relief lengthtapering slightly but otherwise conforming to the shape of the secondlength to permit removal of said tube once it has been rolled to assumethe configuration of the second length of said mandrel.
 2. The mandrelof claim 1 wherein the shape of the second length comprises longitudinalflat portions which extend into the transitional length where theygradually become less and less in width to a point where they taper tozero in the proximity of the first length of said mandrel which iscylindrical.
 3. The mandrel of claim 2 wherein the second lengthcomprises six longitudinal flat portions which cover the entire outersurface of said second length of said mandrel to provide an interiormold for forming a hexagonal tube, said six longitudinal flat portionsgradually tapering to zero through said transitional length of saidmandrel, the total cross-sectional area of said transitional lengthtapering in the opposite direction to said flat portions to provide thetransitional length with a combination of rounded and flat portionsrunning longitudinally throughout said transitional length said roundedportions tapering toward said second length while said flat portionstaper towards said first length.
 4. The mandrel of claim 3 wherein saidlongitudinal flat portions are spiraled through at least saidtransitional length to provide a tube of spiraled hexagonalconfiguration.
 5. The mandrel of claim 2 wherein the second lengthcomprises three longitudinal flat portions which cover the entire outersurface of said second length of said mandrel to provide an interiormold for forming a triangular tube, said three longitudinal flatportions gradually tapering to zero through said transitional length ofsaid mandrel, the total cross-sectional area of said transitional lengthtapering in the opposite direction to said flat portions to provide thetransitional length with a combination of rounded and flat portionsrunning longitudinally throughout said transitional length said roundedportions tapering toward said second length while said flat portionstaper towards said first length.
 6. The mandrel of claim 5 wherein saidflat portions are spiraled to provide a tube which is of spiraledtriangular configuration.
 7. The mandrel of claim 1 wherein said mandrelhas a groove in its second length which gradually diminishes in depththrough said transitional length of said mandrel to a point where saidgroove reaches zero depth in the proximity of said first length of Saidmandrel, said groove causing the formation of a ridge on the inner wallof said tube as it is rolled over the working zone of said mandrel.
 8. Amandrel for use in cold rolling processes to produce tubing with variousinternal configurations comprising: an elongated member adapted forinsertion within a hollow circular tube, said member being tapered andshaped for at least portions of its length, said shaping being for thepurpose of imparting to the interior walls of the hollow circular tubethe shape of said mandrel, said shaping comprising surfacing of saidmandrel so that said mandrel is effectively divided into longitudinalportions, each portion being of the same configuration, althoughgradually increasing in size and pronouncement from the end of themandrel of greatest diameter to the opposite end near the portion of themandrel where the size and shape of said mandrel are used to mold theinterior walls of said tube.